A Twitter user identifying himself as Anonymous Palestine says site flooded until the servers overloaded and crashed in a distributed denial of service attack.

Hackers brought down the websites of Haaretz and Israel Hayom newspapers, as well as the sites of two hospitals - Sheba Medical Center, Tel Hashomer and Assouta Medical Center, Tel Aviv - in the latest cyber attack against Israeli targets.

A Twitter user identifying himself as Anonymous Palestine declared on Wednesday that the two newspaper sites were flooded with data until the servers overloaded and crashed in what is known as a distributed denial of service attack.

The website of the Israel Festival was also vandalized, and there were reports of problems accessing the website of Tel Aviv University.

After the Sheba website was down for a few hours, the hospital announced that its "defense mechanisms responded to the attempts to hack the hospital website, but the millions of requests received simultaneously led to a denial of service.

We are working to identify the sources of these requests to block the hostile activity."

DDoS attackers bombard a site or a server with multiple communication requests, often through a network of computers that the attacker controls without the knowledge of the computers' owners.

Even if the electronic offensive doesn't crash the site or allow it to be hacked, the owner of the site may be forced to shut it to external traffic to prevent damage.

A week and a half ago the websites of El Al and the Tel Aviv Stock Exchange were brought down, a day after hackers calling themselves the Nightmare Group threatened to attack them.

Several Israeli banks have also been subject to such barrages, leading the Bank of Israel to recommend that the banks block access from certain areas of Iran, Saudi Arabia and Algeria. Several banks have simply blocked all Internet access from countries they deem to be high risk.